The present application relates generally to a ramping subsystem for a control system for a machine with a dual path electronically controlled hydrostatic transmission having variable displacement pumps and/or variable displacement motors.
One type of machine with a dual path electronically controlled hydrostatic transmission or a dual path electro-hydraulic transmission that is used for propulsion and steering can be a crawler-tractor such as a bulldozer. “Bulldozers” or “dozers,” as those terms may be used herein, refer to crawler-tractors that are equipped with a blade for scraping the ground or pushing material along the ground. The blade is pivotally connected to the crawler-tractor chassis such that it can pivot up and down. Blade controls are provided to the operator in the cab of the vehicle to permit the operator to raise and lower the blade with respect to the chassis of the crawler-tractor. One of the most common uses for blades on bulldozers is to level or otherwise contour the ground for the construction of houses, buildings, parking lots, and roads.
The hydrostatic transmission of the machine or bulldozer can use one or more pumps and one or more motors controlled by a controller for performing a variety of functions such as the propulsion and steering of the machine or bulldozer and implement operation on the machine or bulldozer. To reduce the rate of change of current commands given to the pump and motor solenoids when the machine or bulldozer is accelerated, decelerated or when the direction of the machine is changed (i.e., from forward to reverse or vice versa), a ramping subsystem or block can be used. There can be three ramping parameters or ramps associated with pump commands to move the machine in a forward or reverse direction: a ramping parameter or ramp that governs a rate of increase in pump command or displacement, a ramping parameter or ramp that governs a rate of decrease in pump command or displacement, and a ramping parameter or ramp that governs the rate of decrease of pump command or displacement only if the operator changes the machine direction. Since each ramping parameter of the ramping subsystem corresponds to a specific time constant, applying that parameter to two different commands having two different maximum magnitudes, but having identical rates of change, would take the same amount of time to achieve their corresponding maximum magnitude from the minimum magnitude which results in an unacceptable machine behavior to the operator driving the machine.
Therefore, what is needed is a ramping subsystem that can modify the rate of change of pump and motor commands based on their maximum magnitude.